There has long been suspicion that the strong lamp illumination required from RTA may nonthermally influence the diffusion of dopants. Here we describe for the first time the dependence of such effects on temperature and illumination intensity. Experiments employ specialized structures composed of isotopically labeled 30Si tracer atoms in an epitaxial 28Si matrix. Illumination enhanced self-diffusion in n-type Si, but appeared not to influence in p-type Si. Illumination intensity threshold increased with temperature and the trend suggests that even at high RTA temperatures (∼1050°C), lamp illumination may influence not only self-diffusion, but also the diffusion of dopant atoms.